给父母申请绿卡# Visa - 签证
m*f
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Consider a function which, for a given whole number n, returns the number of
ones required when writing out all numbers between 0 and n.
For example, f(13)=6. Notice that f(1)=1. What is the next largest n such
that f(n)=n?
ones required when writing out all numbers between 0 and n.
For example, f(13)=6. Notice that f(1)=1. What is the next largest n such
that f(n)=n?